This invention relates generally to photocatalytic air cleaners and, more particularly, to a control system for modulating the operation thereof.
The process of removing or reducing organic pollutants from a fluid by contacting the fluid with a photoreactive metal semiconductor material in the presence of ultraviolet light has long been known. One application is that of detoxifying the air being conditioned and circulated within a building. That is, within the circulation airstream, an ultraviolet (UV) light is caused to radiate a substrate that is coated with a photocatalyst such as titanium dioxide to thereby bring about a photocatalytic oxidation reaction to eliminate undesirable volatile organic compounds (VOC""s) and microbiological contaminants such as bacteria, molds, and viruses that may be in the airstream. Such a process substantially enhances the environmental and health aspects of an air-conditioning system and may even improve the comfort level in the conditioned space.
One approach to operating such a photocatalytic air purifier is to install it into a system in such a way as to have it operating at all times, i.e. with the ultraviolet light being on at all times. While this ensures that the maximum amount of purification will occur, it is also expensive and wasteful since much of that operational time would not be necessary or even effective. For example, during periods in which there is no air flowing over the substrate, such as when the fan is turned off, there would be little or no detoxification occurring and therefore little reason to have the UV lamp on.
Another possibility is that of turning the air purifier on and off with the air-conditioning system. While this will save energy and prolong the life of the UV bulbs, it will still result in the unnecessary use of the air purifier at times when it is not needed and the nonuse of it during periods in which it is needed, such as, for example, when a space has been cooled to a desired temperature but there are still impurities in the air.
It is therefore an object of the present invention to provide a method and apparatus for controlling the operation of a photocatalytic air purifier to obtain effective, efficient and economical use thereof so as to thereby reduce the operational and maintenance costs thereof. This object and other features advantages become more readily apparent upon reference to the following description when taken in conjunction with the appended drawings.
Briefly, in accordance with one aspect of the invention, a photocatalytic air purifier is controlled so as to operate only to the extent necessary as indicated by conditions within a space. The purification process is therefore optimized with respect to efficiency and economy.
In accordance with another aspect of the invention, the extent of the purifier operation is controlled in response to the sensing of certain conditions in the space. For example, a sensor designed to measure the amount of VOC""s or microbiological contaminants is used to control the on/off conditions of the purifier to operate only as necessary to destroy the contaminants that are sensed. When the level of contaminants has been reduced to a predetermined threshold level, the control will automatically shut down the purifier.
By yet another aspect of the invention, the air purification process is controlled not only between the on/off conditions but also by degree of operation. That is, in response to the sensed conditions, the number of UV lamps or the power to the lamps may be selectively varied, for example. Another variable that may be controlled is the xe2x80x9cdwell timexe2x80x9d, which may be varied by controlling the amount of air or the flow of the airstream passing over the air purifier. This can be accomplished by controlling the speed of the fan or the position of the damper.
In the drawings as hereinafter described, a preferred embodiments is depicted; however, various other modifications and constructions can be made thereto without departing from the true spirit and scope of the invention.